Human rights-based approaches to development (HRBADs) have been pointed out as the most accomplished form of integration of human rights in development. Despite the growing talks among development practitioners on the need for human rights-based approaches to development policies and practices, it remains unclear what exactly the human right principle of accountability at the heart of these approaches consists of. This article seeks to unravel some of the difficulties. What does the principle of accountability mean? Who is accountable and to whom? What does it mean for current development practice? Reflecting on these questions, this article critically delves into policy, guidance, operational documents, evaluations, and other analyses by a selected number of bilateral development agencies. This desk-based research is in some cases backed by semi-structured interviews designed to provide a review of the current approaches to applying the principle of accountability. The article sheds light on how the principle of accountability is understood and applied by those agencies, and notes challenges and inconsistencies. It argues that the principle of accountability should be made fit for purpose so as not to become mere political rhetoric without practical meaning in development practice. It is thus contended that development agencies and state donors should move beyond understanding the principle of accountability as one that is grounded in internal accountability mechanisms and systems of evaluation and aim for holding all stakeholders, including themselves, accountable to the rights-holders of their development programmes and projects.